On Wednesday, Jeremy Wright QC MP, the Attorney General of the United Kingdom, gave a speech intended to clarify his government’s understanding of the international law framework governing the use of armed force. The United Nations Charter recognizes the inherent right of States to use force in self-defense “if an armed attack occurs.” Importantly, the UK takes the view that States may use force in anticipatory self-defense to prevent imminent armed attacks before they occur. The Attorney General’s speech discusses the concept of imminence at some length but, in my view, leaves the UK’s position less clear than it was before.
From the outset, the speech fails to distinguish between two very different interpretations of the imminence requirement. The Attorney General says
As you know, any use of force in self-defence under Article 51 must be both necessary and proportionate to the threat. A part of the assessment of necessity, where an attack has not yet taken place, is that the attack must be imminent for states to take action. To put it simply, is action necessary now?
With respect, this passage conflates the imminence of an attack with the immediate necessity of defensive action. The question “Is an attack imminent?” is quite distinct from the question “is defensive action necessary now?”
On one view, international law prohibits the use of defensive force until an armed attack is about to occur. On this view, the lawfulness of defensive force turns on when the armed attack will occur unless it is prevented. On a very different view, international law prohibits the use of defensive force until the last window of opportunity to prevent the armed attack is about to close. On this view, the lawfulness of defensive force turns on when defensive action must be taken for it have a reasonable chance of success.
In many cases, the imminence of an attack and the immediate necessity to take defensive action will coincide. However, in some cases, they may come apart. In some cases, an attack will occur quite soon (say, in a matter of hours), but there will be a clear opportunity to prevent the attack until minutes before it is launched (say, by a drone hovering overhead). In other cases, an armed attack will not occur soon, but the last clear opportunity to prevent the attack may be about to end. For example, suppose that State A is preparing to send an armed group that it directs and controls into State B in order to carry out a series of armed attacks. State B can prevent these attacks by striking the armed group while it is assembled in State A, but not after it disperses to enter State B. For a more colorful hypothetical case, see here.
In my view, the Attorney General should have distinguished between the imminence of an armed attack and the immediate necessity of defensive action, and explained which of these two standards determines the lawfulness of defensive force.
In a later passage, the Attorney General says that
The principles of the modern law on imminence are almost universally accepted as having their origins in the diplomatic correspondence of 1842 following the Caroline Incident five years earlier . . . .
On the contrary, the International Law Commission takes the view that the Caroline incident has no direct relevance to the modern law of self-defense. But leave that aside. The Attorney General goes on to say that
Imminence was described in the Caroline case as a threatened attack which was “instant, overwhelming, leaving no choice of means, and no moment of deliberation.”
This is not correct. The relevant letter refers to “a necessity of self-defence, instant, overwhelming, leaving no choice of means, and no moment for deliberation.” As Marty Lederman explains in a Just Security post, this passage is not concerned with the imminence of an attack but instead with the immediate necessity of preventive action.
Finally, the Attorney General says
In each exercise of the use of force in self-defence, the UK asks itself the questions that flow from [Daniel Bethlehem’s] articulation. Questions like – how certain is it that an attack will come? How soon do we believe that attack could be? What scale of attack is it likely to be? Could this be our last clear opportunity to take action? And crucially – is there anything else we could credibly do to prevent that attack?
As we have seen, the questions in bold are quite distinct from one another. Yet this passage gives no indication of how the UK understands their relationship. Is an imminent attack necessary for lawful defensive force? Or is it sufficient that the last clear opportunity to take action is about to close? In my view, the Attorney General failed to answer these vitally important questions.